src/time/strftime.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <string.h>
   4 #include <langinfo.h>
   5 #include <locale.h>
   6 #include <time.h>
   7 #include <limits.h>
   8 #include "locale_impl.h"
   9 #include "libc.h"
  10 #include "time_impl.h"
  11
  12 char *__nl_langinfo_l(nl_item, locale_t);
  13
  14 static int is_leap(int y)
  15 {
  16         /* Avoid overflow */
  17         if (y>INT_MAX-1900) y -= 2000;
  18         y += 1900;
  19         return !(y%4) && ((y%100) || !(y%400));
  20 }
  21
  22 static int week_num(const struct tm *tm)
  23 {
  24         int val = (tm->tm_yday + 7U - (tm->tm_wday+6U)%7) / 7;
  25         /* If 1 Jan is just 1-3 days past Monday,
  26          * the previous week is also in this year. */
  27         if ((tm->tm_wday + 371U - tm->tm_yday - 2) % 7 <= 2)
  28                 val++;
  29         if (!val) {
  30                 val = 52;
  31                 /* If 31 December of prev year a Thursday,
  32                  * or Friday of a leap year, then the
  33                  * prev year has 53 weeks. */
  34                 int dec31 = (tm->tm_wday + 7U - tm->tm_yday - 1) % 7;
  35                 if (dec31 == 4 || (dec31 == 5 && is_leap(tm->tm_year%400-1)))
  36                         val++;
  37         } else if (val == 53) {
  38                 /* If 1 January is not a Thursday, and not
  39                  * a Wednesday of a leap year, then this
  40                  * year has only 52 weeks. */
  41                 int jan1 = (tm->tm_wday + 371U - tm->tm_yday) % 7;
  42                 if (jan1 != 4 && (jan1 != 3 || !is_leap(tm->tm_year)))
  43                         val = 1;
  44         }
  45         return val;
  46 }
  47
  48 const char *__tm_to_tzname(const struct tm *);
  49 size_t __strftime_l(char *restrict, size_t, const char *restrict, const struct tm *restrict, locale_t);
  50
  51 const char *__strftime_fmt_1(char (*s)[100], size_t *l, int f, const struct tm *tm, locale_t loc, int pad)
  52 {
  53         nl_item item;
  54         long long val;
  55         const char *fmt = "-";
  56         int width = 2, def_pad = '0';
  57
  58         switch (f) {
  59         case 'a':
  60                 if (tm->tm_wday > 6U) goto string;
  61                 item = ABDAY_1 + tm->tm_wday;
  62                 goto nl_strcat;
  63         case 'A':
  64                 if (tm->tm_wday > 6U) goto string;
  65                 item = DAY_1 + tm->tm_wday;
  66                 goto nl_strcat;
  67         case 'h':
  68         case 'b':
  69                 if (tm->tm_mon > 11U) goto string;
  70                 item = ABMON_1 + tm->tm_mon;
  71                 goto nl_strcat;
  72         case 'B':
  73                 if (tm->tm_mon > 11U) goto string;
  74                 item = MON_1 + tm->tm_mon;
  75                 goto nl_strcat;
  76         case 'c':
  77                 item = D_T_FMT;
  78                 goto nl_strftime;
  79         case 'C':
  80                 val = (1900LL+tm->tm_year) / 100;
  81                 goto number;
  82         case 'e':
  83                 def_pad = '_';
  84         case 'd':
  85                 val = tm->tm_mday;
  86                 goto number;
  87         case 'D':
  88                 fmt = "%m/%d/%y";
  89                 goto recu_strftime;
  90         case 'F':
  91                 fmt = "%Y-%m-%d";
  92                 goto recu_strftime;
  93         case 'g':
  94         case 'G':
  95                 val = tm->tm_year + 1900LL;
  96                 if (tm->tm_yday < 3 && week_num(tm) != 1) val--;
  97                 else if (tm->tm_yday > 360 && week_num(tm) == 1) val++;
  98                 if (f=='g') val %= 100;
  99                 else width = 4;
 100                 goto number;
 101         case 'H':
 102                 val = tm->tm_hour;
 103                 goto number;
 104         case 'I':
 105                 val = tm->tm_hour;
 106                 if (!val) val = 12;
 107                 else if (val > 12) val -= 12;
 108                 goto number;
 109         case 'j':
 110                 val = tm->tm_yday+1;
 111                 width = 3;
 112                 goto number;
 113         case 'm':
 114                 val = tm->tm_mon+1;
 115                 goto number;
 116         case 'M':
 117                 val = tm->tm_min;
 118                 goto number;
 119         case 'n':
 120                 *l = 1;
 121                 return "\n";
 122         case 'p':
 123                 item = tm->tm_hour >= 12 ? PM_STR : AM_STR;
 124                 goto nl_strcat;
 125         case 'r':
 126                 item = T_FMT_AMPM;
 127                 goto nl_strftime;
 128         case 'R':
 129                 fmt = "%H:%M";
 130                 goto recu_strftime;
 131         case 's':
 132                 val = __tm_to_secs(tm) - tm->__tm_gmtoff;
 133                 width = 1;
 134                 goto number;
 135         case 'S':
 136                 val = tm->tm_sec;
 137                 goto number;
 138         case 't':
 139                 *l = 1;
 140                 return "\t";
 141         case 'T':
 142                 fmt = "%H:%M:%S";
 143                 goto recu_strftime;
 144         case 'u':
 145                 val = tm->tm_wday ? tm->tm_wday : 7;
 146                 width = 1;
 147                 goto number;
 148         case 'U':
 149                 val = (tm->tm_yday + 7U - tm->tm_wday) / 7;
 150                 goto number;
 151         case 'W':
 152                 val = (tm->tm_yday + 7U - (tm->tm_wday+6U)%7) / 7;
 153                 goto number;
 154         case 'V':
 155                 val = week_num(tm);
 156                 goto number;
 157         case 'w':
 158                 val = tm->tm_wday;
 159                 width = 1;
 160                 goto number;
 161         case 'x':
 162                 item = D_FMT;
 163                 goto nl_strftime;
 164         case 'X':
 165                 item = T_FMT;
 166                 goto nl_strftime;
 167         case 'y':
 168                 val = (tm->tm_year + 1900LL) % 100;
 169                 if (val < 0) val = -val;
 170                 goto number;
 171         case 'Y':
 172                 val = tm->tm_year + 1900LL;
 173                 if (val >= 10000) {
 174                         *l = snprintf(*s, sizeof *s, "+%lld", val);
 175                         return *s;
 176                 }
 177                 width = 4;
 178                 goto number;
 179         case 'z':
 180                 if (tm->tm_isdst < 0) {
 181                         *l = 0;
 182                         return "";
 183                 }
 184                 *l = snprintf(*s, sizeof *s, "%+.4ld",
 185                         tm->__tm_gmtoff/3600*100 + tm->__tm_gmtoff%3600/60);
 186                 return *s;
 187         case 'Z':
 188                 if (tm->tm_isdst < 0) {
 189                         *l = 0;
 190                         return "";
 191                 }
 192                 fmt = __tm_to_tzname(tm);
 193                 goto string;
 194         case '%':
 195                 *l = 1;
 196                 return "%";
 197         default:
 198                 return 0;
 199         }
 200 number:
 201         switch (pad ? pad : def_pad) {
 202         case '-': *l = snprintf(*s, sizeof *s, "%lld", val); break;
 203         case '_': *l = snprintf(*s, sizeof *s, "%*lld", width, val); break;
 204         case '0':
 205         default:  *l = snprintf(*s, sizeof *s, "%0*lld", width, val); break;
 206         }
 207         return *s;
 208 nl_strcat:
 209         fmt = __nl_langinfo_l(item, loc);
 210 string:
 211         *l = strlen(fmt);
 212         return fmt;
 213 nl_strftime:
 214         fmt = __nl_langinfo_l(item, loc);
 215 recu_strftime:
 216         *l = __strftime_l(*s, sizeof *s, fmt, tm, loc);
 217         if (!*l) return 0;
 218         return *s;
 219 }
 220
 221 size_t __strftime_l(char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm, locale_t loc)
 222 {
 223         size_t l, k;
 224         char buf[100];
 225         char *p;
 226         const char *t;
 227         int pad, plus;
 228         unsigned long width;
 229         for (l=0; l<n; f++) {
 230                 if (!*f) {
 231                         s[l] = 0;
 232                         return l;
 233                 }
 234                 if (*f != '%') {
 235                         s[l++] = *f;
 236                         continue;
 237                 }
 238                 f++;
 239                 pad = 0;
 240                 if (*f == '-' || *f == '_' || *f == '0') pad = *f++;
 241                 if ((plus = (*f == '+'))) f++;
 242                 width = strtoul(f, &p, 10);
 243                 if (*p == 'C' || *p == 'F' || *p == 'G' || *p == 'Y') {
 244                         if (!width && p!=f) width = 1;
 245                 } else {
 246                         width = 0;
 247                 }
 248                 f = p;
 249                 if (*f == 'E' || *f == 'O') f++;
 250                 t = __strftime_fmt_1(&buf, &k, *f, tm, loc, pad);
 251                 if (!t) break;
 252                 if (width) {
 253                         /* Trim off any sign and leading zeros, then
 254                          * count remaining digits to determine behavior
 255                          * for the + flag. */
 256                         if (*t=='+' || *t=='-') t++, k--;
 257                         for (; *t=='0' && t[1]-'0'<10U; t++, k--);
 258                         if (width < k) width = k;
 259                         size_t d;
 260                         for (d=0; t[d]-'0'<10U; d++);
 261                         if (tm->tm_year < -1900) {
 262                                 s[l++] = '-';
 263                                 width--;
 264                         } else if (plus && d+(width-k) >= (*p=='C'?3:5)) {
 265                                 s[l++] = '+';
 266                                 width--;
 267                         }
 268                         for (; width > k && l < n; width--)
 269                                 s[l++] = '0';
 270                 }
 271                 if (k > n-l) k = n-l;
 272                 memcpy(s+l, t, k);
 273                 l += k;
 274         }
 275         if (n) {
 276                 if (l==n) l=n-1;
 277                 s[l] = 0;
 278         }
 279         return 0;
 280 }
 281
 282 size_t strftime(char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm)
 283 {
 284         return __strftime_l(s, n, f, tm, CURRENT_LOCALE);
 285 }
 286
 287 weak_alias(__strftime_l, strftime_l);